The ruling overturns a previous decision of the District Court for the Northern District of California.
The software in question allows train hobbyists to control model trains via a computer. At issue in the suit was the right of persons to exercise an Artistic Licence (an open source licence) over publicly sourced materials.
Matthew Katzer was accused of altering Robert Jacobsen's open source software without crediting its creator or indicating how the software had been altered.
The case, Jacobsen v Katzer, is the first time the CAFC has directly stated that violation of an open source licence can be deemed copyright infringement.
Although the issue has been dealt with before by US courts, Michael Bennett of Wildman Harrold said that this case is the first one that has provided clarity: "The problem [with past cases] is that they have left the question open because they were settled or they were decided on grounds that didn't include open source licensing."
"Now, with licences that are similar to [the one in this case], the plaintiffs have a remedy available to them without [having to make] some of those arguments that are very difficult to prove," he added.
The precedent set by the verdict could have an impact on General Public Licence (GPL) proceedings as well.
"There are several actions that are continuing on in other venues and it gives the plaintiffs ready-made arguments that they are entitled to injunctive relief," said Bennett. "The court gave deference to the wording of the Artistic Licence, and the GPL version [uses] similar wording."
The CAFC said that Katzer's violation of the licence amounted to copyright infringement in part because the licence included the words "provided that", which denoted certain conditions for use of the software.
In its opinion the Court said: "The Artistic License states on its face that the document creates conditions: 'The intent of this document is to state the conditions under which a Package may be copied.' The Artistic License also uses the traditional language of conditions by noting that the rights to copy, modify, and distribute are granted 'provided that the conditions are met.' Under California contract law, 'provided that' typically denotes a condition."
Despite the ruling, some practitioners think open source licences will still be difficult to enforce going forward. "There are a couple of questions that remain," said James Gatto of Pillsbury Winthrop Shaw Pittman. "I think it's still going to be fact-specific. I don't think this is a per se rule."
Gatto added: "The second thing is that the remedy people are looking for in open source licence infringement is not monetary damages, but compliance. One of the big questions still is how do you measure damages for copyright infringement [in these cases]?"
But others see the verdict as a vindication. "We're completely thrilled with the decision," said James Vasile of the Software Freedom Law Center in New York. "It provides yet another example of enforcement of an open source licence and puts all future enforcements on more solid footing."
